1. Field of the Invention
The present invention relates to a visual acuity testing apparatus for examining visual performance of a subject's eyes according to subjective determination of a subject.
2. Description of the Related Art
There is disclosed in JP2002-143092A, for example, a visual acuity testing apparatus for examining visual performance of a subject's eyes according to the response of a subject, so as to determine the refractivity of eyeglass lenses when making eyeglasses.
Such a visual acuity testing apparatus includes a target presenting unit for presenting various targets to the subject's eye, an optical element arrangement device, and a controller for controlling the operation of the target presenting unit and the optical element arrangement device. The optical element arrangement device includes a plurality of corrective lenses of optical elements for correcting the visual performance of the subject's eye, and selectively disposes between the subject's eye and the target presenting unit a corrective lens having refractive power according to the response from the subject. With this visual acuity testing apparatus, plural types of examinations can be conducted, and each of the examinations can be performed by using a target set for each of the examinations.
The controller includes an operation section which is operated for selecting the target to be presented to the subject's eye and the corrective lens, a display section for displaying the operation contents of the operation section, and a memory in which target data showing each of the targets and operation image data showing an operation image to be displayed onto the display section are stored. The controller also includes an arithmetic control section for extracting the target data corresponding to the target selected by the operation of the operation section and the operation image data from the memory, and an output section for outputting to the display section image signals indicating the operation image corresponding to the operation image data extracted by the arithmetic control section. The arithmetic control section sends driving control signals for displaying the target corresponding to the extracted target data to the target presenting unit.
The target presenting unit includes a memory, a plurality of target plates, a control section, and an arrangement device. The target data identical to the target data stored in the memory of the controller is stored in the memory. Each of the target plates includes targets corresponding to the target data stored in the memory. The control section extracts from the memory the target data of the driving control signals from the arithmetic control section of the controller. The arrangement device is driven for selectively arranging in front of the subject's eye the target plate corresponding to the target data extracted by the control section.
When examining the visual performance of a subject's eyes, at first, an examiner selects a target having a type corresponding to an examination type by the operation of the controller. The arrangement device is driven by the driving control signal received from the arithmetic control section of the controller, and the target plate corresponding to the target indicated by the driving control signal is thereby disposed in front of the subject's eyes. Next the examiner asks the subject about the visibility of the target when the subject looks at the target of the target plate via the corrective lens, and switches the corrective lens to a corrective lens corresponding to the vision ability of the subject's eye according to the response from the subject. The visual performance of the subject's eye is thereby corrected, and the value of the refractive power of the eyeglasses is determined.
However, since the target presenting unit for presenting each of the targets to the subject includes the memory in which the target data identical to the target data stored in the memory of the controller is stored and a plurality of target plates onto which the targets corresponding to the targets stored in the memory are marked, for example, when adding new target data into the memory of the controller, or changing the existing target data to the new target data, it is necessary to newly add into the memory of the target presenting unit the target data identical to the target data newly added into the memory of the controller and to newly add into the target presenting unit the target plate onto which the targets corresponding to the added target data are marked, or to change the target data of the memory of the target presenting unit to the target data identical to the target data of the memory of the controller and to change the target plate to a new target plate, in order to match the target types presentable in the target presenting unit with the target types selectable by the controller. For this reason, the operation for incorporating a new target into the visual acuity testing apparatus becomes complicated.